@perpou,
Welcome to Q4OS.
I can probably provide you with answer to your question number 2. Yes, it is possible to resize your Q4OS partition using Gparted, however you have to do it form a live CD or USB stick image not form installed Q4OS. You should bear in mind that there is always the possibility of losing data when you do that.
Also, if you install Windows after installing any linux distribution, you will lose the option of booting into Q4OS as Windows operating system will over write the GRUB and consequently your boot menu. So, I recommend you set up your partitions using Gpartd from a live CD/USB, install Windows first if you must, then install Q4OS.